1. Field of the Invention
The present invention relates to an image pickup apparatus that performs binning processing of obtaining a binning pixel signal by adding up pixel signals.
2. Description of the Related Art
Since image pickup devices of recent years have been increased in the number of pixels and highly densified, and in particular, an image pickup device that is adopted in an electronic endoscope system is also downsized, an area of one pixel has become small, and it is sometimes difficult to ensure brightness of an image sufficiently.
In relation to this, as an art of increasing brightness of an image, an art called binning is proposed, which obtains a pixel value corresponding to one pixel by adding up pixel values obtained from a plurality of adjacent pixels.
For example, Japanese Patent Application Laid-Open Publication No. 2008-72501 describes the art of adding (simple addition, or ratio addition which multiplies peripheral pixels by a ratio of equal to or less than one and adding the peripheral pixels) peripheral pixels having the same color to an pixel of interest, with respect to a video signal that is outputted from an image pickup device and converted into a digital signal. The Publication further describes the art of changing the number of added pixels that is the number of the pixel of interest and peripheral pixels which are targets to be added in accordance with a luminance distribution.
More specifically, in order to reduce a whiteout or black crushing of an image plane, the pixel addition method described in the publication splits an image into a plurality of regions and detects the brightness of the pixel of interest in each of the respective regions, and determines the number of added pixels in binning processing on the basis of the detection result of the brightness, and when the luminance of a region is a predetermined threshold value or more at this time, pixel addition processing is not performed (that is, only the pixel of interest is used).